Genetic analysis of durable adult plant stripe rust resistance in durum wheat cultivars

The deployment of combinations of resistance genes in commercial cultivars is necessary to achieve sustained disease control. Old American durum cultivars Wells and Leeds as well as Australian cultivars Yallaroi and Wollaroi are susceptible to Australian Puccinia striiformis f. sp. tritici pathotypes 110 E143A+ and 134 E16A+ at the seedling stage. These cultivars produced low stripe rust responses at the adult plant stage since their release and therefore were chosen for genetic analysis. Genetic analyses of adult plant stripe rust resistance using Wells/Bansi and Leeds/Bansi F3 populations indicated the involvement of two independent genes each in Wells and Leeds. These genes produced intermediate adult plant stripe rust responses when present singly. Absence of segregation among F3 lines derived from crosses of older north American cultivars Leeds and Wells with Australian cultivars Wollaroi and Yallaroi indicated the presence of common gene(s) for stripe rust resistance. Common parentage of these cultivars supported this conclusion and suggested narrow genetic base of stripe rust resistance among Australian and old American durum wheat cultivars. The effectiveness of both old and modern cultivars over two and four decades, respectively, indicated durable nature of the genes carried by these cultivars.